Twenty or 30 years ago, the components for EV conversions were quite a bit less sophisticated,
but one problem didn't often present itself - vacuum for power brakes. Most hobbyists converted
small cars. They were light and easy to stop. Many didn't even have power brakes when they
left the factory.
In the last few decades cars have pudged out. Now almost all of them have power brakes - and
need them.
When you convert one, you need something to replace the ICE vacuum that previously eased your
right-foot chore, or you may find yourself gliding through stop signs.
So when you convert the car, you have to provide some source of vacuum for the power brakes.
The traditional answer, used in conversions for decades, is a Gast or other commercial 12 volt
vacuum pump. It's not really an EV part, but it does the job. It'll need an external reservoir,
a vacuum switch, and usually a relay. Most of the EV parts suppliers offer pumps and complete
kits. The cost is around $350-400 for a kit, around $275-300 for a bare pump.
The Swiss-made MES-DEA
vacuum pump is smaller, lighter, and quieter than the Gast pumps. It's a one-piece, bolt-in system
specifically designed for conversion EVs. The vacuum switch is built in. It doesn't have a
vacuum reservoir, but a quick and dirty answer is to fix several feet of vacuum hose on the
hose barb and wind it round the pump. Unfortunately this pump is now tough to
find, even in Europe.
So we arrive at our prime subject: the GM vacuum pump. It was
fitted to several models of 1980s-vintage GM cars whose engines didn't produce enough
vacuum to make the power brake servo happy.
You'll probably want to look for a boneyard pump first. But these pumps have been out of production
for many years now. If you can find one, make sure you test it before you buy it.
The following GM cars had this pump:
Buick Skyhawk 1982
Buick Skylark 1982-5
Cadillac Cimmaron 1982
Chevrolet Celebrity 1984-6
Chevrolet Caprice 1982
Chevrolet Cavalier 1982
Olds Cierra 1986
Olds Firenza 1982
Olds Omega 1985-6
Pontiac 6000 1985-6
Pontiac J2000 1982
Pontiac Phoenix 1982-4
You'll find the pump on the driver's side front fender well. There's a small carbon filter on the line just before the pump - make
sure you get it. You also want the electrical plug that goes to the pump and the rubber mounting plate. You may have to go out in
the yard with the torch jockey to show him what you're talking about.
From left to right on the lugs, the first lug is 12 volt power, UNswitched. The second one from the left is ignition switch or toggle.
-
Connection A (Red wire) battery positive, 12 volts+ through a fuse.
-
Connection B (Black with white stripe) ignition positive, 12 volts+
-
Connection C (plugged) not used (not used in factory system either)
-
Connection D (Black wire) ground, 12 volts-
The pump is powered via the A connection, but will only run if it
receives power from the ignition switch on the B connection.
The pump was at one time available new from GM parts counters, as part number 22034995. It seems to be a
discontinued item now, but you may be able to find old dealer stock.
